Move Builders for CameraCharacteristics and CaptureResult

As internal Builders of the objects they create.

Test: atest virtual_camera_tests
Test: atest CtsVirtualDevicesCameraTestCases
Bug: 429128545
Bug: 371167033
Flag: android.companion.virtualdevice.flags.virtual_camera_metadata
Change-Id: Idd5197885dec35de8a4b5e4bdd03ca2175aac784